Microwave Active Filter Design

A simplified method for the project and design of microwave active filters is presented here. The presented design is based on the use of an active inductor that emulates an inductor behavior by implementing a passive variable phase- and amplitude-compensating network and amplifiers, forming a gyrator-C architecture. This method can be applied with success for the design of bandpass filters with very high performances in terms of integration and application from a few hundreds of MHz to tens of GHs with filter high dynamic range and frequency tuning capability

Design and characterisation of electromagnetic bandgap filters

Most signal processing / communications applications heavily rely on filters. For adaptive spectrum filtering and for applications that switch between sets of different filter implementations, it would be beneficial to utilize just one, tuneable band-pass filter. In recent years, the study of metamaterials emerged as an area of scientific research due to the unique attributes of metamaterials. Metamaterials typically are artificial structures with properties not found in nature, for instance negative refraction indexes. Their feature sizes span a fraction of the wavelength corresponding to their frequency of operation. A sub group of metamaterials, the electromagnetic bandgap (EBG) structures, exhibit stopbands for electromagnetic waves irrespective of polarization or angle of incidence. EBG structures prominently achieved surface wave suppression to minimise cross talk between neighbouring devices and improving antenna efficiency by acting as a perfect magnetic conductor within a certain frequency range. The thesis investigates the suitability of EBG structures for filter implementations. The goal is to provide a tuneable band-pass filter for adaptive spectrum filtering and communication applications. The bandgap of an infinite array of EBG cells is numerically determined. Based on those results, an EBG band-pass filter implementation on a printed circuit board (PCB) is designed, fabricated and characterized. Different tuning methods were incorporated into the PCB design to create a tuneable EBG band-pass filter. An EBG filter was built on a fused silica wafer, in order to shift the passband to higher frequencies

Tunable C Band Coupled-C BPF with Resonators using Active Capacitor and Inductor

In this thesis, a classic second-order coupled-capacitor Chebyshev bandpass filter with resonators using active capacitor and inductor is presented. The low cost and small size of CMOS active components makes the band pass filter (BPF) attractive in fully-integrated CMOS applications. The active capacitor is designed to compensate active inductor\u27s resistance for resistive match in the resonator. Meanwhile, adjusting design parameter of the active component provides BPF tunability in center frequency, pass band and pass band gain. Designed in 1.8V 180 nanometer CMOS process, the BPF has a tuning frequency range of 758-864 MHz, a controllable pass band of 7.1-65.9 MHz, a Q factor of 12-107, a pass band gain of 6.5-18.1dB and a stopband rejection of 38-50 dB

A Tunable Electromagnetic Band-gap Microstrip Filter

In high frequency design, harmonic suppression is a persistent struggle. Non-linear devices such as switches and amplifiers produce unwanted harmonics which may interfere with other frequency bands. Filtering is a widely accepted solution, however there are various shortcomings involved. Suppressing multiple harmonics, if desired, with traditional lumped element and distributed component band-stop filters requires using multiple filters. These topologies are not easily made tunable either. A new filter topology is investigated called Electromagnetic Band-Gap (EBG) structures. EBG structures have recently gained the interest of microwave designers due to their periodic nature which prohibits the propagation of certain frequency bands. EBG structures exhibit characteristics similar to that of a band-stop filter, but in periodically repeating intervals making it ideal for harmonic suppression. The band-gap frequency of an EBG structure may be varied by altering the periodicity of the structure. However, EBG materials are generally static in structure making tuning a challenge. In this thesis, a novel solution for tuning the band-gap properties of an EBG structure is investigated. Designs aimed to improve upon existing solutions are reached. These designs involve acoustic and mechanical tuning methods. Performance is simulated using Agilent’s Advanced Design System (ADS) and a device is constructed and evaluated. Comparing all measured test cases to simulation, band-gap center frequency error is on average 4.44% and absolute band-gap rejection error is 1.358 dB

A Variable Bandwidth, Power-Scalable Optical Receiver Front-End

The tremendous growth in internet data traffic and computation power has increased demand for high-speed links in almost all communication systems. Normally, high-speed interconnects in a super computer are implemented using a short distance electrical medium such as a printed circuit board or coaxial cable. However, data transmission through an electrical medium suffers severe bandwidth limitation due to its distributed resistance, inductance and capacitance. To overcome this problem, several equalization techniques are adopted which can make the system more complex and power hungry. An efficient way to enhance the capacity of short-reach link is through the use of an optical channel rather than the band-limited electrical one. The analog front-end is the most important building block of the optical receiver as it converts the small current generated by the photodiode to a significant voltage level. In this work, we present an inductor-less, variable bandwidth, power-scalable optical receiver front-end in TSMC 65nm and 90nm CMOS with two different topologies. The front-end contains a transimpedance amplifier (TIA) and post amplifiers (PA) in 90 nm CMOS (Design 1) whereas in 65 nm CMOS (Design 2) an offset compensation block and a transconductor is incorporated to improve the robustness of the overall receiver front-end.The transimpedance amplifier in both designs is implemented with the shunt feedback topology and the post amplifiers in 90 nm and 65 nm design use the common source topology loaded with modified active inductors and the Cherry-Hooper inverter based topology, respectively. In order to make the receiver front-end power and bandwidth scalable, a current controlling PMOS array and a tuneable resistive bank is implemented in both designs. The Design 1 is able to vary the supported data rate from 1.25 Gb/s to 15 Gb/s. The gain at each data rate is ~ 84 dBΩ. The overall power dissipation varies from 0.94 mW to 7.46 mW as the data rate scales, maintaining an energy per bit lower than 800 fJ at all data rates using a 1.2 V power supply. The input referred noise density varies from 4.31 pA/√Hz to 14.27 pA/√Hz. In the Design 2, the receiver front-end can be tuned from 1.25 Gb/s to 20 Gb/s maintaining a fixed gain of ~75 dBΩ. The power dissipation in this case varies from 0.32 mW to 13.5 mW as the data rate scales up, maintaining energy per bit less than 700 fJ using a 1 V power supply. The input referred noise density varies from 8.46 pA/√Hz to 18 pA/√Hz. Simulation shows that Design 1 is not robust enough against the mismatch and global process variations whereas Design 2 is much more robust against these effects. This type of front-end has applications in links that vary data rate in response to system requirements. Additionally, the lowest data rate can be act as an idle mode which receives data used only to maintain transmitter and receiver synchronization

Conducting metal oxide materials for printed electronics

Printed electronics as a manufacturing process has many advantages, mainly, it allows for the high throughput rapid fabrication of thin, flexible electronic components with minimal waste. There are many printing processes that can be utilised for printing electronics and although each process can differ vastly, the materials currently used in these processes are generally the same, silver and carbon. However, to develop printing as a more mainstream manufacturing method for electronics, a wider variety of materials are required which can provide better stability and longevity of components, new functionality for printed applications and allow for in-situ processing and tuning of components. Conducting metal oxides are a good candidate for integrating into printed electronics processes, these materials are typically semiconductors, they have bandgaps, and properties can be altered via altering the band gap. They are also oxides, so they cannot oxidise further and therefore atmospheric damage is reduced compared to pure metals. They can also be fabricated into a wide range of particle morphologies, all with advantages in different fields and electronic applications. Therefore, the ability to print these materials is valuable to the field. In this thesis, the integration of conducting metal oxide electro-ceramic materials into the field of printed electronics has been explored. This was performed through the completion of five research objectives including, the selection of appropriate materials for the research, the formulation of conductive inks with the materials, the investigation of post-processing techniques for printed films and further research into passive component fabrication and sensor applications. Firstly, following an extensive literature review, four materials were selected including three doped zinc oxide materials synthesised via different methods. The fourth material is commercially sourced indium tin oxide (ITO). A nitrocellulose vehicle was determined to be the most compatible with the oxides and selected for ink formulation. Inks were then formulated with all four materials, with optical and electrical properties analysed. Gallium doped Zinc Oxide (GZO) and ITO were selected for further investigation based on the excellent conductivity of the indium tin oxide (57.77Ω□-1) and the highly transparent optical properties of the gallium doped zinc oxide (>84% transmittance). Laser processing was selected as a post processing method. It was found that the laser processing dramatically increased conductivity. The GZO improving from a non-conductive film to 10.21% of bulk conductivity. The ITO improved from 3.46% to 40.47% of the bulk conductivity. It was also found that the laser processing invoked a carbothermal reduction process allowing for a rapid manufacturing process for converting spherical particles into useful nanoparticle morphologies (nanorods, nanowires etc). Following this, resistive and capacitive applications involving laser processing and conventionally heat-treated conductive oxide inks were developed. Combining the new materials and manufacturing processes, tuneable printed resistors with a tuning range of 50 to 20M could be fabricated. All metal oxide, ITO based capacitors were also fabricated and characterised. These were then developed into humidity sensors which provided excellent humidity sensing properties, showing linearity between 5 and 95% relative humidity (RH) and sensitivities of up to 7.76pF/RH%, demonstrating higher performance than commercial equivalents (0.2 – 0.5pF/RH%). In conclusion, this work provides a breakthrough for conductive metal oxide materials research and its place in Printed Electronics research by providing insight into the processes required to make these materials conduct and by developing useful manufacturing methods, post processing techniques and applications.</div

Design and simulation of a low-cost biosensor for point-of-care diagnose devices

The principal aim of the work is to help in the development of a low-cost biosensor capable of providing a reliable diagnosis to inexpert users. Rather than being a precise measurement instrument like mass spectrometers, this biosensor should be able to qualitatively detect and distinguish between the most relevant families of the bacteria causing mycobacterium tuberculosis in human fluids. Other approaches pursue outstanding sensitivity relying on expensive materials and microfabrication processes. Despite other requisites, low-cost imposes certain criteria regarding materials, systems, fabrication techniques and user interfaces to be included in the device.Ingeniería Biomédic

Robust direct acoustic impedance control using two microphones for mixed feedforward-feedback controller

This paper presents an acoustic impedance control architecture for an electroacoustic absorber combining both a feedforward and a feedback microphone-based strategies on a current-driven loudspeaker. Feedforward systems enable good performance for direct impedance control. However, inaccuracies in the required actuator model can lead to a loss of passivity, which can cause unstable behaviors. The feedback contribution allows the absorber to better handle model errors and still achieve an accurate impedance, preserving passivity. Numerical and experimental studies were conducted to compare this new architecture against a state-of-the-art feedforward control method

A new configuration for shunt active power filters

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This thesis presents a new power circuit configuration to be used in shunt active power filters. A new control algorithm based on the linear voltage control suitable for the proposed circuit is introduced. The system is analysed both in time and frequency domains. The practical implementation of the system proves its suitability for the proposed task. The switching frequency of the proposed circuit is much lower than that in other active filters. The switching losses are then considerably reduced, in addition to the fact that the switching devices can withstand larger values of currents being switched on and off at lower frequencies which is an advantage to this circuit. The component sizes (capacitors and inductors) in the proposed circuit are also much smaller than those in other filter configurations. In addition, the thesis presents a new method for categorising the active filter systems proposed in the surveyed literature. The survey includes a comparison of these techniques showing their respective merits and drawbacks. The thesis also includes an implementation of a reference current generator that is suitable for single-phase applications without the need for excessive computations. The technique involves a modified Fourier analysis, which is suitable for active filtering applications